JP2008110609A - White laminated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a white laminated polyester film excellent in weather resistance, whiteness and adhesiveness with an accepting layer. <P>SOLUTION: The white laminated polyester film of two or more layers having at least a white polyester layer (A) and a white polyester layer (B) is characterized by that a yellowing degree caused by an ultraviolet ray irradiation according to JIS K-7103, measured from the white polyester layer (A) side is 45 or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a white laminated polyester film.

  More specifically, the present invention relates to a white laminated polyester film that is excellent in weather resistance and whiteness and is suitable as a base material for a receiving sheet used in various printing records such as inkjet, thermal transfer, and offset printing.

Conventionally, a white laminated polyester film in which inorganic fine particles such as calcium carbonate and barium sulfate are contained in polyester has been used as a substrate for various applications, particularly printing recording such as ink jet, thermal transfer, and offset printing. .

  Furthermore, in recent years, there has been an increasing demand for weather resistance in many film applications, but in response to such a demand, an ultraviolet absorber or the like is included in the film, or an ultraviolet absorber or the like is added by coating or coextrusion. A film having a weather resistance layer further improved by laminating the contained weather resistance layer on the surface is known. As such a weather-resistant film, for example, those described in JP-B-60-17696, JP-A-56-13163 and the like are known.

  However, since the white laminated polyester film is used as a substrate for outdoor use such as a marking film, a poster, an electric signboard, etc., when using the above-described technology to impart weather resistance, it contains an ultraviolet absorber, etc. Problems such as a decrease in whiteness due to coloring, bleeding out of the UV absorber over time, and a decrease in adhesiveness with the receiving layer provided on the white laminated polyester film when used as a receiving sheet.

  On the other hand, in order to avoid the above-mentioned problem, when the ultraviolet absorber is not contained, the weather resistant layer is not laminated, or the content of the ultraviolet absorber is reduced, the weather resistance is insufficient, so that fading or discoloration occurs. It was easy to cause the characteristic fall accompanying with.

  An object of the present invention is to provide a white laminated polyester film that solves the above-described problems, retains a high degree of weather resistance, and has excellent whiteness and adhesion to a receiving layer. .

  The white laminated polyester film of the present invention that achieves this object is a white laminated polyester film of at least two layers having at least a white polyester layer (A) and a white polyester layer (B), and the white polyester layer (A) side. It is a white laminated polyester film characterized by having a yellowing degree by ultraviolet irradiation of 45 or less according to JIS K-7103.

  The white laminated polyester film of the present invention is excellent in weather resistance, storage stability, and adhesion to the receiving layer, and can exhibit clean whiteness, so it is used as a base material for receiving sheets based on whiteness. Can give a high-class image.

  Since the white laminated polyester film of the present invention has the excellent characteristics as described above, it can be suitably used as a base material for a receiving sheet used for various printing records such as ink jet, thermal transfer, offset printing, and particularly a marking film. It is optimally used for outdoor substrates such as posters, posters, and signboards.

  The white laminated polyester film of the present invention needs to have a laminated structure of two or more layers having at least a white polyester layer (A) and a white polyester layer (B). For example, when the effect of the present invention is to be obtained with a single-layer film, the film is easily broken and the film forming property is unstable, resulting in an increase in cost. Therefore, a layered structure of two or more layers, the white polyester layer (A) is allowed to exhibit various properties such as weather resistance, whiteness, optical density, etc., and the white polyester layer (B) is a layer with better film formation stability, and // By using a layer having properties other than the above properties, the entire white laminated polyester film can satisfy all necessary properties.

  In the present invention, the polyester is a polymer obtained by condensation polymerization from a diol and a dicarboxylic acid, and the dicarboxylic acid is represented by terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid and the like. The diol is typified by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol and the like. Specifically, for example, polyethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylenedimethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate and the like can be used. In the present invention, polyethylene terephthalate and polyethylene naphthalate are particularly preferable.

Of course, these polyesters may be homopolyesters or copolyesters, and examples of copolymer components include diol components such as diethylene glycol, neopentyl glycol, polyalkylene glycol, adipic acid, sebacic acid, Dicarboxylic acid components such as phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 5-sodium sulfoisophthalic acid can be used. In addition, in this polyester, if necessary, an appropriate additive in an amount that does not impair the effects of the present invention, such as a heat stabilizer, an oxidation stabilizer, an anti-wrinkle stabilizer, an organic lubricant, an organic type Fine particles, fillers, antistatic agents, nucleating agents, dyes, dispersants, coupling agents and the like may be blended.

  The polyester used in the present invention is preferably polyethylene terephthalate. Polyethylene terephthalate film is excellent in water resistance, durability, chemical resistance and the like.

  The white laminated polyester film in the present invention is required to have a yellowing degree of 45 or less, preferably 40 or less according to JIS K-7103, measured from the white polyester layer (A) side. Furthermore, it is most preferable that it is 35 or less. When the degree of yellowing is greater than 45, the whiteness is deteriorated due to discoloration by ultraviolet irradiation, particularly yellowing, and the weather resistance when used as a base material for outdoor use is insufficient, so that the quality of the printed image may be deteriorated. is there. The yellowing degree in the present invention represents yellowing on the plus side and whitening with bluishness on the minus side, and its lower limit is not particularly limited, but is substantially zero.

  The white polyester layer (A) in the present invention is a polyester layer containing white dye or inorganic fine particles or the like, or innumerable fine bubbles are generated in the layer, and light is emitted by the fine bubbles. It is a layer that is made white opaque by scattering and also has weather resistance.

  Among the whitening methods, inorganic fine particles are preferably added to the polyester in terms of weather resistance, stability over time, and optical density. As the inorganic fine particles, those having at least the surface of titanium oxide, zinc oxide or cerium oxide are preferable from the viewpoint of imparting weather resistance.

  Examples of such inorganic fine particles include titanium oxide, zinc oxide or cerium oxide, or zinc carbonate, calcium carbonate, magnesium carbonate, magnesium oxide, silica, talc, kaolin, lithium fluoride, calcium fluoride, barium sulfate. Zinc sulfide, alumina, calcium phosphate, mica or the like is used as a core layer (core), and a titanium oxide or zinc oxide layer is provided on the surface by coating or the like. These may be used alone or in combination of two or more.

  In the present invention, among these particles, it is more preferable to use titanium oxide-based particles particularly from the standpoint of comprehensive effects such as whiteness, optical density, and weather resistance.

  In addition, the inorganic fine particles may be in the form of a porous or hollow porous material, and further in order to improve the dispersibility with respect to the resin within the range where the effects of the present invention are not hindered. It may be given.

  In the present invention, when the white polyester layer (A) is whitened by containing the inorganic fine particles described above, the surface particle gap inside the white polyester layer (A) is 0.3 μm in terms of weather resistance. Or less, more preferably 0.2 μm or less, and most preferably 0.15 μm or less. When the surface particle gap is larger than 0.3 μm, the effect when using the inorganic fine particles is low, and the weather resistance may be inferior. The lower limit is not particularly limited, but substantially 0 can be said to be the lower limit.

The average particle size of the inorganic fine particles in the present invention is preferably 0.05 to 3 μm,
What is in the range of 0.07-1 micrometer is more preferable. If the average particle size is outside the above range, uniform dispersion becomes difficult, the smoothness of the film surface is deteriorated, and further, the whiteness and weather resistance may decrease due to these, which is not preferable. .

  The amount of inorganic fine particles added is not particularly limited, but is preferably 1 to 35% by weight, more preferably 5 to 30% by weight, and most preferably 7 to 25% by weight. When the amount added is less than the above range, it is difficult to improve the properties of the film such as whiteness, optical density, and weather resistance. Inconvenience such as powder generation may occur.

  Further, in the present invention, the whiteness decreases due to coloring, the ultraviolet absorber bleeds with time, and when used as a receiving sheet, the adhesiveness with the receiving layer provided on the white laminated polyester film decreases. In order to further improve the weather resistance, it is preferable that an ultraviolet absorber is contained in the white polyester layer (A) within a range in which no problem such as occurrence occurs.

In the present invention, the content of the ultraviolet absorber in the white polyester layer (A) is:
It is preferably 5% by weight or less, more preferably 3% by weight or less, and most preferably 1% by weight or less. Further, the lower limit of the content is not particularly limited, but is substantially 0. When the content of the ultraviolet absorber exceeds 5% by weight, the above problem may occur.

  The ultraviolet absorber used in the present invention is preferably one that is excellent in heat resistance, has good compatibility with the above-described polyester, can be uniformly dispersed, and has little coloration and does not adversely affect the resin. In particular, a weight reduction temperature of 5% by weight of an ultraviolet absorber that is a measure of heat resistance is preferably 250 ° C. or more in terms of film forming properties and film characteristics.

  As an ultraviolet absorber, various things, such as a benzophenone series, a benzotriazole series, a hindered amine series, can be used, for example, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, 2,2′-4,4′-tetrahydroxy-benzophenone, 2,2′-dihydroxy-4,4′-dimethoxy-benzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, 2 , 2′-dihydroxy-4-methoxybenzophenone, 2,4-di-tert-butylphenyl-3 ′, 5′-di-tert-butyl-4′-hydroxybenzoate, 2,2′-methylenebis [4- ( 1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2 -Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-t-octylphenol) benzotriazole, 2- (3 ', 5'-diterariamil-2'-hydroxyphenyl) benzo Triazole, 2 (2′-hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzo Triazole, 2-ethoxy-2′-ethyl oxac acid bisanilide, 2,4-di-t-butylphenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate, bis (2,2 , 6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2-hydroxyethyl) -4-hydro Shi-2,2,6,6-tetramethylpiperidine polycondensate and the like can be used. Among them, 2,2 ′, 4,4′-tetrahydroxy-benzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, and 2,2′-methylenebis excellent in compatibility with polyester are preferable. [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol].

  The ultraviolet absorber is not particularly limited, and may be used alone or in combination of two or more in some cases.

  In the present invention, a fluorescent whitening agent may be added to the white polyester layer (A) in order to give the white laminated polyester film of the present invention a high-grade image color exhibiting clearer whiteness and bluishness. desirable.

  The fluorescent whitening agent absorbs ultraviolet rays in sunlight or artificial light, maintains the function of radiating it into violet to blue visible light, and lowers the brightness of the polymer substance by its fluorescence action. It is a compound that promotes whiteness without any problems. Examples of fluorescent brighteners include “Ubitec” (Ciba-Geigy), “OB-1” (Eastman), “TBO” (Sumitomo Seika Co., Ltd.), and “Kaycoal” (Nippon Soda Co., Ltd.). “Kayalite” (Nippon Kayaku Co., Ltd.), “Lyukopua” EGM (Client Japan Co., Ltd.) and the like can be used. The fluorescent brightening agent is not particularly limited, and may be used alone or in combination of two or more depending on the case. However, in the present invention, it is particularly excellent in heat resistance and has good compatibility with the above polyester and is uniform. It is desirable to use a material that can be dispersed, has little coloration, and does not adversely affect the resin.

  The content of the fluorescent brightener in the white polyester layer (A) is preferably 0.005 to 1% by weight, and more preferably 0.05 to 0.5% by weight. When the content is less than the above range, it is difficult to obtain a sufficient whitening effect, and those exceeding the above range are not preferable because uniform dispersibility and whiteness are easily lowered.

  The white laminated polyester film of the present invention has a laminated structure of two or more layers having at least a white polyester layer (A) and a white polyester layer (B), and the white polyester layer (B) has fine bubbles. For example, when used as a base material for receiving sheets such as ink jet and thermal transfer, the layer that has been included provides flexibility and cushioning to improve printability and transferability, or reduce the weight of the base material. It is more preferable when aiming at. As a method of adding fine bubbles, there are a method of generating fine bubbles by adding a foaming agent and fine particles and / or adding a thermoplastic resin incompatible with polyester and uniaxially or biaxially stretching it. Generally, it is preferable to use a thermoplastic resin incompatible with the polyester.

  The said thermoplastic resin as used in the field of this invention is thermoplastic resins other than polyester, and resin incompatible with polyester is preferable. Such a resin refers to a glass transition temperature (hereinafter referred to as “Tg”) corresponding to polyester in a system in which polyester and the thermoplastic resin are melted in measurement using a method such as a differential scanning calorimeter (DSC). In addition to the above, Tg corresponding to the thermoplastic resin is observed.

  A thermoplastic resin that is incompatible with polyester has a great effect of dispersing in the form of particles in the polyester and forming voids in the polyester film by stretching.

  The melting point of such a thermoplastic resin is preferably lower than the melting point of the polyester and higher than the temperature used for orienting the film support. From this point, among the thermoplastic resins, olefin polymers such as polyethylene, polypropylene, polybutene and polymethylpentene or copolymers thereof are preferable.

  Among them, polypropylene and polymethylpentene having a small critical surface tension are preferable, and polymethylpentene is particularly preferable because it has a large surface tension difference from polyester and has a high melting point, so that fine bubbles can be easily formed during stretching. Further, when a thermoplastic resin is used in combination with an olefin polymer or copolymer having a polar group such as a carboxyl group or an epoxy group or a functional group reactive with polyester, a polyalkylene glycol, etc., the dispersion diameter of the thermoplastic tree Is smaller, and the voids by stretching can be made finer, and the surface roughness is also reduced.

  The content of the thermoplastic resin incompatible with the polyester in the white polyester layer (B) is not particularly limited, but is preferably 1 to 35% by weight, and more preferably 3 to 20% by weight. When the amount added is less than the above range, it is difficult to improve the properties of the film such as whiteness, optical density, and weather resistance. On the other hand, when the amount is more than the above range, problems such as film breakage during stretching occur. There is a case.

  In the present invention, the white polyester layer (B) is mainly composed of a polyester resin and inorganic fine particles, and the content (% by weight) of the inorganic fine particles in the white polyester layer (B) is the white polyester layer ( A) having a configuration smaller than that in the middle is more preferable in terms of improving the film forming property and reducing the weight. In this case, the difference in the content of inorganic fine particles between the white polyester layer (A) and the white polyester layer (B) is preferably 2 to 30% by weight, more preferably 2 to 25% by weight, and most preferably 3 to 20%. % By weight.

  When the difference in content is less than the above range, the effect when the content is different is small, and as a result, the cost of the laminated structure may increase.

  On the other hand, when the difference in content is larger than the above range, the smoothness of the film surface may be deteriorated, and inconvenience such as generation of powder during post-processing may occur, which is not preferable.

  In the present invention, the white polyester layer (A) and the white polyester layer (B) may be the same polyester composition or different polyester compositions. In particular, when different polyester compositions, for example, the white polyester layer is a homopolyester and the polyester layer (A) is a copolyester, it is more preferable because properties such as easy adhesion can be obtained. In addition, when the polyester used for the white polyester layer (A) is polyethylene naphthalate and the polyester used for the white polyester layer (B) is polyethylene terephthalate, it is preferable because improvement effects such as weather resistance and rigidity are obtained.

  Furthermore, the white laminated polyester film of the present invention is obtained by laminating the white polyester layer (A) on both sides of the white polyester layer (B) to form a three-layer laminated structure, such as characteristics such as whiteness, concealability, and weather resistance. And more desirable from the point of practicality.

  In the present invention, as a method of laminating the white polyester layer (A) and the white polyester layer (B), a method of compounding by co-extrusion during melt film formation, or a method of laminating after forming each film separately. Any of the methods may be used, but the former method is more preferable in terms of cost and the like.

  In the white laminated polyester film of the present invention, the whiteness obtained from the white polyester layer (A) side is 80% or more, more preferably 85% or more, and most preferably 90% or more. It is preferable because it shows beautiful whiteness.

  Moreover, it is preferable that the optical density of the white laminated polyester film of this invention is 0.6 or more and 1.8 or less. More preferably, it is 0.8 or more and 1.5 or less. If the optical density is less than 0.6, the concealing property of the film is small, and the back side can be seen through, which is not preferable. Moreover, in order for the optical density to exceed 1.8, a large amount of particles must be contained, and the strength of the film may be reduced, which is not preferable.

  Further, the white laminated polyester film of the present invention has excellent smoothness when the surface gloss obtained from the white polyester layer (A) side is 45% or more, more preferably 50% or more, most preferably 60% or more. When used as a base material for a receiving sheet, a high-definition image can be formed, which is preferable.

Further, in the present invention, the thickness of the white laminated polyester film is not particularly limited, but those in the range of usually 10 to 500 μm, preferably about 20 to 300 μm are excellent in practical handling as a base film. Therefore, it is preferable. Of these, the thickness of the white polyester layer (A) is preferably from 0.5 to 50 μm, more preferably from 1 to 25 μm. When the laminated thickness is outside the above range, sufficient weather resistance is difficult to obtain, and whiteness may be lowered.

  Next, some examples of the method for producing the white laminated polyester film and the receiving sheet of the present invention will be described, but the present invention is not limited to such examples.

  Regarding the method for producing a white laminated polyester film, in a composite film forming apparatus having an extruder (A) and an extruder (B), the polyester chip and the inorganic microparticle master chip are 1 to 35% by weight of the inorganic microparticles. After being mixed and sufficiently dried under vacuum, it is fed to an extruder (A) heated to 270 to 300 ° C. Moreover, in order to laminate the white polyester layer (B), a separately dried polyester chip and an inorganic fine particle and / or a mixture of polyester and an incompatible thermoplastic resin that are 1 to 35% by weight are extruded. Is supplied to the machine (B) and laminated in a T-die composite die so that the polymer of the extruder (A) is on the surface layer (one side) or both surface layers (both sides) of the extruder (B). A molded laminated sheet is obtained by molding.

  The melted laminated sheet is closely cooled and solidified by static electricity on a drum cooled to a surface temperature of 10 to 60 ° C. to produce an unstretched film. The unstretched film is led to a roll group heated to 80 to 120 ° C., stretched 2 to 5 times in the longitudinal direction (longitudinal direction, that is, the traveling direction of the film), and cooled with a roll group of 20 to 30 ° C.

  Subsequently, the film stretched in the longitudinal direction is guided to the tenter while being gripped by clips, and is stretched in the direction perpendicular to the longitudinal direction in an atmosphere heated to 90 to 140 ° C.

  The stretching ratio is 2 to 5 times in the longitudinal and lateral directions, and the area ratio (longitudinal stretching ratio x lateral stretching ratio) is preferably 6 to 20 times. If the area magnification is less than 6 times, the resulting film has insufficient whiteness. Conversely, if the area magnification exceeds 20 times, the film tends to be broken during stretching.

In order to give the flatness and dimensional stability of the biaxially stretched film thus obtained,
The white laminated polyester film of the present invention can be obtained by heat setting at 150 to 230 ° C. in a tenter, uniformly cooling and then cooling to room temperature and winding.

  The white laminated polyester film thus obtained is excellent in weather resistance, adhesion to the receiving layer and whiteness, and gives a high-class image when used as a receiving sheet base material based on whiteness. Therefore, it can be suitably used as a base material for receiving sheets used for various printing records such as inkjet, thermal transfer, and offset printing, and is especially suitable for outdoor base materials such as marking films, posters, and electrical signs. Used.

[Measurement and evaluation method of characteristics]
The characteristic values used in the description of the present invention are based on the following evaluation method and evaluation criteria.

(1) Average particle diameter and surface particle gap of particles Using a transmission electron microscope HU-12 type (manufactured by Hitachi, Ltd.), the cross section of the white polyester layer (A) was enlarged 3,000 to 200,000 times. It was determined from the observed cross-sectional photograph. That is, the particle portion of the cross-sectional photograph is marked, and the particle portion is subjected to image processing using a high-definition image analysis processing apparatus PIAS-IV (manufactured by Pierce Co., Ltd.), and a total of 100 particles in the measurement field of view are true. The average diameter when converted to a circle was calculated and used as the average particle diameter of the particles. Further, the width of the portion not containing the inorganic fine particles in the direction perpendicular to the film plane in the range of 5 μm from the outermost surface portion of the white polyester layer (A) was read to obtain the surface particle gap. In addition, it calculated | required as an average value of ten places in a measurement visual field.

(2) Yellowing degree An ultraviolet irradiation test of 2 cycles of irradiation (irradiation 16 hours) was performed under the following conditions using an ultraviolet deterioration accelerating tester iSuper UV Tester SUV-W131 (manufactured by Iwasaki Electric Co., Ltd.). Next, for the white laminated polyester film before and after the ultraviolet irradiation, the tristimulus value of the color was measured according to JIS Z-8722 using a spectroscopic color difference meter (SE-2000 manufactured by Nippon Denshoku Industries Co., Ltd.), The degree of yellowing was determined according to JIS K-7103.

"UV irradiation conditions"
One cycle of irradiation is 8 hours (illuminance: 100 mW / cm ² , temperature and humidity: 60 ° C. × 50% RH), 4 hours (temperature / humidity: 35 ° C. × 100% RH (condensation)).

(3) Whiteness Measured according to JIS L-1015 using UV-260 manufactured by Shimadzu Corporation. When the reflectances at wavelengths of 450 nm and 550 nm are B% and G%, respectively, the whiteness is expressed by the following formula.

Whiteness (%) = 4B-3G
(4) Concealment property It was determined by optical density and measured using an optical densitometer (TR927 manufactured by Macbeth).

  The greater the measured value, the higher the concealability.

(5) Adhesive The white polyester layer (A) side of the present invention is coated with a reverse coater so that the thickness after drying of the following receiving layer-forming coating solution is 10 μm as a receiving layer suitable for the ink jet system, After drying at 130 ° C. for 1 minute to provide a receiving layer, “Scotch” mending tape (manufactured by Sumitomo 3M Co., Ltd.) is applied to the receiving layer, and the remaining property of the receiving layer after T-peeling is visually observed. The following three-stage evaluation was performed. ○ The above was considered good.

"Receptive layer forming coating solution"
A. Hydrophilic resin: polyvinyl alcohol resin aqueous coating solution (obtained by heating and dissolving a polyvinyl alcohol resin having a saponification degree = 78 mol% and a molecular weight = 500 with hot water at 80 ° C. for 30 minutes and cooling to room temperature)
B. Cationic resin: Saftomer ST-2100 (Mitsubishi Oil Chemical Co., Ltd.) A / B was mixed at a solid content weight ratio of 50/50 and diluted with water to a solid content concentration of 15% by weight.

"Adhesion evaluation"
○: The receiving layer hardly transfers to the tape.

    Δ: Part of the receiving layer peels off.

    X: The receiving layer peels in a planar shape.

  The present invention will be described with reference to the following examples and comparative examples, but the present invention is not limited thereto.

Example 1
A raw material obtained by adding 17% by weight of anatase-type titanium oxide fine particles having an average particle size of 0.3 μm to a polyethylene terephthalate (hereinafter abbreviated as “PET”) chip is dried at 180 ° C. for 3 hours and then supplied to an extruder (A). Then, it was melted at 285 ° C. by a conventional method and introduced into a T-die composite die.

  On the other hand, 5% by weight of polymethylpentene (hereinafter abbreviated as “PMP”) and 1% by weight of polyethylene glycol (hereinafter abbreviated as “PEG”) having a molecular weight of 4000 as a compatibilizer were added to the PET chip. After drying at 180 ° C. for 3 hours, the product is fed to an extruder (B) and melted at 285 ° C. by a conventional method. A laminated melt sheet laminated on the surface layer was obtained.

  The laminated melt sheet was closely cooled and solidified by an electrostatic charge method on a cooling drum maintained at a surface temperature of 25 ° C. to obtain an unstretched film. Subsequently, the unstretched film was stretched 3.2 times in the longitudinal direction using a roll group heated to 98 ° C. according to a conventional method, and cooled with a roll group at 25 ° C.

  Further, the stretched film was led to a tenter and stretched 3.4 times in a direction perpendicular to the longitudinal direction in an atmosphere heated to 125 ° C. Thereafter, the film is heat-set at 220 ° C. in a tenter and uniformly cooled and wound up to obtain a white laminated polyester film having a thickness of 100 μm, wherein the white polyester layer (A) is 5 μm and the white polyester layer (B) is 90 μm. It was.

  The properties of the white laminated polyester film thus obtained are as shown in Table 1. It has excellent weather resistance with a yellowing degree of 9.9, excellent whiteness, expresses cushioning properties, and is flexible. It was rich.

Example 2
As a raw material supplied to the extruder (A) of Example 1, the addition amount of anatase-type titanium oxide is 25% by weight, and as a raw material supplied to the extruder (B), an addition amount of anatase-type titanium oxide is 14% by weight. The white laminated polyester film was obtained by the same method as Example 1 except having used what was made. The characteristics of this white laminated polyester film are as shown in Table 1, and were excellent in each characteristic, particularly excellent in weather resistance and whiteness.

Examples 3 and 4
Based on Examples 1 and 2, as raw materials to be supplied to each extruder (A), a benzotriazole UV absorber “Adekastab” LA having a 5% weight loss temperature of 372 ° C. in the raw materials of Examples 1, 2 and 3 A white laminated polyester film was obtained in the same manner as in Examples 1 and 2, except that -31 (manufactured by Asahi Denka Kogyo Co., Ltd.) was added at 0.8% by weight per resin. The characteristics of the white laminated polyester film were excellent in each characteristic as shown in Table 1, and particularly excellent in weather resistance.

Examples 5 and 6
Based on Examples 1 and 2, as a raw material to be supplied to each extruder (A), 0.12% by weight of an optical brightener “OB-1” (manufactured by Eastman) was added to the raw materials of Examples 1 and 2. A white laminated polyester film was obtained in the same manner as in Examples 1, 3, and 5 except that the added one was used. The characteristics of this white laminated polyester film were excellent in each characteristic as shown in Table 1, and particularly excellent in bluish whiteness.

Comparative Example 1
The raw material supplied to the extruder (A) of Example 1 was replaced with Example 1 except that 14% by weight of calcium carbonate fine particles having an average particle diameter of 0.5 μm were added instead of anatase-type titanium oxide. A white laminated polyester film was obtained by the same method.

  As shown in Table 1, the white laminated polyester film had a yellowing degree of 49.6 and poor weather resistance.

Comparative Example 2
Example 1 except that 18 wt% of barium sulfate fine particles having an average particle diameter of 0.2 μm were added to PET chips as raw materials to be supplied to the extruder (A) and the extruder (B) of Example 1. A white laminated polyester film was obtained by the same method.

  As shown in Table 2, the properties of the white laminated polyester film were excellent in weather resistance, but inferior in whiteness and adhesiveness with the receiving layer.

Comparative Examples 3 and 4
As a raw material to be supplied to the extruder of Comparative Example 2, 20% by weight of polypropylene (hereinafter abbreviated as “PP”) added to PET chip (Comparative Example 3), polystyrene (hereinafter abbreviated as “PSt”) A white laminated polyester film was obtained in the same manner as in Comparative Example 2 except that 15% by weight (Comparative Example 4) was used.

  As shown in Table 1, the characteristics of the white laminated polyester film were inferior in weather resistance.

Comparative Example 5
As a raw material to be supplied to the extruder of Comparative Example 2, a benzotriazole ultraviolet absorber “Adekastab” LA-31 (Asahi Denka Kogyo Co., Ltd.) having a weight loss temperature of 372 ° C. of 5% by weight is resin. A white laminated polyester film was obtained in the same manner as in Example 1 except that 8% by weight was added.

  Using this white laminated polyester film, a receiving layer was prepared in the same manner as in Example 1 to prepare a receiving sheet.

  As shown in Table 1, the properties of this receiving sheet were excellent in weather resistance, but inferior in whiteness and adhesiveness between the receiving layer and the white laminated polyester film as the substrate.

Claims (11)

Two or more layers of white laminated polyester film having at least a white polyester layer (A) and a white polyester layer (B), and measured by ultraviolet irradiation according to JIS K-7103 measured from the white polyester layer (A) side. A white laminated polyester film having a yellowing degree of 45 or less. The white laminated polyester film according to claim 1, wherein the white polyester layer (A) comprises a polyester resin and inorganic fine particles as main components. The white laminated polyester film according to claim 2, wherein at least the surface of the inorganic fine particles is titanium oxide or zinc oxide. The white laminated polyester film according to claim 2 or 3, wherein a gap between surface particles inside the white polyester layer (A) is 0.3 µm or less. The white laminated polyester film according to claim 1, 2, 3 or 4, wherein the content of the ultraviolet absorbent in the white polyester layer (A) is 5% by weight or less. 6. The white laminated polyester film according to claim 1, wherein the white polyester layer (A) contains a fluorescent brightening agent. The white laminated polyester film according to claim 1, 2, 3, 4, 5 or 6, wherein the white polyester layer (B) contains fine bubbles. 8. The white laminated polyester film according to claim 7, wherein the white polyester layer (B) contains a thermoplastic resin incompatible with the polyester. The white laminated polyester film according to claim 8, wherein the thermoplastic resin incompatible with polyester is polyolefin. The white polyester layer (B) is mainly composed of a polyester resin and inorganic fine particles, and the content (% by weight) of the inorganic fine particles in the white polyester layer (B) is more than in the white polyester layer (A). The white laminated polyester film according to claim 2, wherein the white laminated polyester film is less. It has a three-layer laminated structure, the core layer part is a white polyester layer (B), and both surface layer parts are polyester layers (A), The 1, 2, 3, 4, 5, 6, 7 characterized by the above-mentioned. A white laminated polyester film according to claim 8, 9, or 10.